This diary was kept by Nathaniel Ober from 15 May - 3 September 1775. Ober, a shoemaker, served as a member of John Mansfield's Massachusetts Regiment.  (This regiment was recruited in southeastern Essex County and was taken into the Continental Army when it formed in June 1775.)  Although his entries describe events and army life during the Siege (including a description of the Battle of Bunker Hill, the arrival of Gen. Washington at Cambridge, the desertion of soldiers, and military punishments), on many days Ober simply writes, "nothing remarkab[le] today."

Ober’s diary continues many years after his active duty in the army ceased. The diary was used as an account book to record labor conducted and monetary transactions. The first of these begins on page 21 and is dated 29 November 1775. On the following page, dated 10 February 1776, Ober, documents his work mending shoes for many individuals. As this was still within the dateline of the Siege it is possible his work benefited the Continental Army.

This collection includes a letter from Nathaniel Ober's brother, Josiah, expressing his concern for Nathaniel's safety during the Siege of Boston. The letter is dated 20 days after the last entry in Nathaniel Ober's diary.